Starter/Generator Control Module

WARNING: This page is about a different variant/trim than selected.

The starter/generator control module is a multifunction module that is involved in many eAssist system operations. The starter/generator control module contains two internal microprocessors: a battery control processor and a motor control processor. The battery control processor is responsible for the following:

Communicating with the battery energy control module to determine the status of the high voltage battery
Controlling the battery and starter/generator cooling systems
Controlling the main and pre-charge contactors
Monitoring the high voltage interlock loops
Monitoring for isolation faults
Supplying 12 V to the vehicle

Internal to the starter/generator control module, the motor control processor is responsible for propulsion activities and the 14 V control module is responsible for maintaining 12 V to the vehicle. The starter/generator control module may also be referred to as the following names:

SGCM
Hybrid Powertrain Control Module (HPCM)
Accessory Power Module (APM)
Battery Power Inverter Module (BPIM)
Power Inverter Module (PIM)

Hybrid/EV Battery Control

The starter/generator control module interfaces with the battery energy control module to determine the status of the battery voltage and battery temperature. The starter/generator control module uses voltage information from the battery energy control module to make decisions about the battery state of health, how the battery should be charged or discharged, and when to initiate cell balancing.

Hybrid/EV Battery and Starter/Generator Cooling

The starter/generator control module uses temperature information from the battery energy control module to control the hybrid/EV battery pack cooling fan. The starter/generator control module also monitors the starter/generator coolant temperature sensor and will control the starter/generator coolant pump relay, which controls the starter/generator coolant pump.

High Voltage Contactors

At times, it may be necessary to disconnect high voltage from the vehicle, both during normal operation and when a system fault is identified. The starter/generator control module controls the main contactor and pre-charge contactor to disconnect and connect high voltage from the vehicle.

High Voltage Interlock

The high voltage interlock is a fail-safe to disable high voltage when the starter/generator control module identifies that a high voltage area has been accessed. The hybrid/EV battery pack has a high voltage interlock switch located on the service access cover. The starter/generator also has a high voltage interlock switch on the access cover. When either cover is removed, the interlock loop is opened. The starter/generator control module will open the contactors to prevent technician contact with high voltage.

High Voltage Isolation

The starter/generator control module monitors the electrical potential between high voltage and the vehicle chassis. High voltage should always be isolated from the vehicle chassis by a certain amount of resistance to avoid the potential for a life threatening current path. In the event that a high voltage leak path is detected to the vehicle chassis, the starter/generator control module will set a DTC and open the contactors to remove high voltage.

Testing for loss of isolation requires special tools and procedures. Because of the high voltages present in the hybrid system, a loss of isolation may occur due to insulation breakdown. Insulation breakdown typically occurs only when high voltage is present. Conditions such as insulation breakdown cannot be diagnosed with a typical DMM because high voltage is not used by the DMM when measuring resistance.

12 V Output

The starter/generator control module essentially takes the place of the generator on a traditional vehicle. The starter/generator control module converts high voltage DC to a 12 V DC for accessory electrical operation and to charge the 12 V battery.